You walk into the emergency room, clutching your right side in pain. When the ER doctor examines your belly, she suspects you have appendicitis. But she wants to confirm the diagnosis before sending you for surgery. Or maybe your son falls off the high playground bars, and while he has a good-sized bump on his head, he seems otherwise fine. Should either of you have a computed tomography exam – a CT scan? As with any medical test or procedure, there's a risk-benefit balance to consider.

Radiation Risk Some 75 million CT scans are done each year in the United States – and they're great diagnostic tools. A CT exam uses a specialized type of X-ray and a rotating scanner to take a variety of images from different angles around your body. CT exams rapidly produce clear, detailed, cross-sectional pictures. They facilitate diagnosis and treatment of trauma, cancers, cardiovascular disease, infections and congenital conditions, some life-threatening.

But the test itself may pose a health risk. CT scans use ionizing radiation, a known (although relatively weak) carcinogen. Research suggests that CT scans may raise cancer risk – although it would still be very low – particularly in childhood. In addition, studies find radiation doses used in CT vary widely among facilities, even for the same procedure on similar patients.